1. Field of the Invention
The present invention relates to an electrical power system for recharging batteries. More specifically, the power system utilizes a power source which is configured to provide a first output voltage that is lower than a minimum required input voltage for recharging a battery.
2. Description of the Related Art
Rechargeable batteries for providing renewable sources of direct current (DC) electric power are well known in the prior art and are particularly well suited for use with electronic devices, such as a portable drills, video cameras, etc, because the batteries are relatively small and light weight. However, when a rechargeable battery runs low on charge, the electronic device being powered by the battery typically is removed from service while the battery is being recharged or until a charged replacement battery is connected to the device. This results in the inability of an operator to use the electronic device while the battery is being recharged or requires that the operator keep at least one substitute battery available for use, e.g. a fully charged battery, when the first battery is being recharged. However, since the cost of a rechargeable battery can be significant, keeping two or more batteries adapted for use with each electronic device can be cost prohibitive.
Rechargeable batteries typically are recharged by relatively-high voltage power sources, e.g. power sources possessing higher output voltages than the batteries to be charged, such as AC/DC converters or relatively-high voltage output batteries. Neither the AC/DC converters nor the high output batteries, however, are particularly well suited for use in charging batteries in remote locations, such as at a campsite, for instance, because the AC/DC converters require an alternating current power source, which may not be readily accessible, and the high output batteries typically are large, heavy and, otherwise, difficult to transport to the remote locations.
Fuel cells also are well known in the prior art and it is generally known that the smaller the fuel cell, the smaller the potential electric output of the fuel cell. The problem of small fuel cells producing small electric outputs typically has been addressed by connecting a fuel cell to one or more batteries which are configured to provide power for supplementing the electric output of the fuel cell when required. In this manner, when an electronic device being powered by a fuel cell requires more power than the fuel cell is capable of providing, such as during start-up of the fuel cell, the battery is utilized to provide the requisite power. Additionally, when the electronic device being powered by the fuel cell requires less power than the fuel cell is capable of providing, the battery is recharged by the excess electrical power of the fuel cell. For example, U.S. Pat. No. 3,823,358, issued to Rey, and U.S. Pat. No. 5,139,894, issued to Mizuno, disclose power systems configured in this manner.
Other prior art fuel cell power systems, such as disclosed in U.S. Pat. No. 4,670,702, issued to Yamada, incorporate a fuel cell, a battery and a controller. During warm up of the fuel cell of the Yamada device, the controller allows fuel cell output to charge the battery. As the fuel cell reaches operating temperature, the controller allows the battery to discharge to load, thereby reducing the required output of the fuel cell to maintain the load. The fuel cell is then utilized as the primary source of power until the fuel cell is shut down, then the controller once again allows fuel cell output to charge the battery.
In the aforementioned prior art power systems, the fuel cell is the primary DC power source for powering an electronic device. Additionally, the power output of each fuel cell is utilized for recharging its respective battery; therefore, these systems only are adapted to provide recharging power to batteries which require a recharging voltage that is less than or equal to the output voltage of the fuel cell or of the output voltages of multiple fuel cells arranged in series. This limitation often necessitates the use of larger fuel cells so that the required output voltage for battery recharging can be produced.
Therefore, there is a need to provide electrical power systems which overcome these and other shortcomings of the prior art.